1. Field of the Invention
The present invention relates to a spindle motor, and more specifically to a storage disk drive apparatus provided with the spindle motor.
2. Description of the Related Art
Conventionally, a spindle motor for rotating a storage disk is installed within a housing of a storage disk drive apparatus such as a hard disk drive or the like is known. In such a storage disk drive apparatus, a printed circuit board is arranged outside the housing and used for controlling the power supplied to the spindle motor and the operation of the spindle motor. The printed circuit board is electrically connected to the stator of the spindle motor accommodated within the housing. In such a spindle motor, a portion of the printed circuit board is arranged in a recess portion formed on the lower surface of the housing in an effort to reduce the thickness of the spindle motor and the storage disk drive apparatus.
In such an arrangement, conductive wires of the stator are drawn from the recess portion to the lower surface of the housing through a hole formed through the housing. Then the conductive wires are led to the lower surface of the printed circuit board via a through hole of the printed circuit board and are connected to electrodes provided on the lower surface of the printed circuit board.
A flexible printed circuit board is used as the printed circuit board in, e.g., a disk drive apparatus disclosed in Japanese Patent Laid-open Publication No. 2001-67775. The flexible printed circuit board is attached to a housing with a stepped portion to extend along the lower surface of the housing. In this disk drive apparatus, a guide hole, through which a coil line of a stator is drawn, is formed in a bottom wall portion of a bracket of a spindle motor that forms a portion of the housing. A coil line insertion hole communicating with the guide hole is formed at the center of a land portion of the flexible printed circuit board attached to the lower surface of the bracket. The coil line is drawn to the outside through the guide hole and the coil line insertion hole and is soldered to the land portion. At this time, the coil line insertion hole is closed by a solder to seal off the housing, thereby preventing an external air from entering the housing.
In case of the disk drive apparatus disclosed in Japanese Patent Laid-open Publication No. 2001-67775, however, there is a possibility that the sealing reliability may deteriorate due to a time-dependent change of the solder or other causes.
The flexible printed circuit board extends from the recess portion of the housing toward the external region thereof where the flexible printed circuit board is connected to other circuit boards. When sealing the guide hole and the coil line insertion hole with a sealant, there is a need to keep the sealant from flowing out to the external region.
Also, in accordance with an increased reduction in a thickness of the disk drive apparatus, there is a demand for a further reduction in a thickness of a base plate. As mentioned above, a recess portion in which a portion of the flexible printed circuit board is arranged is defined in a lower surface of the base plate. In addition, a variety of recess portions are defined in an upper surface of the base plate to accommodate components of the motor. This, in combination with the reduced thickness of the base plate as a whole, results in some specific areas of the base plate becoming extremely thin. Such extremely thin areas may decrease the rigidity of the base plate so greatly as to induce a vibration in the rest of the motor.